1. Industrial Field of the Invention
The present invention relates to a filler neck cap of a fuel tank for automobiles or the like and, more particularly, to a safety plastic filler neck cap containing positive-negative pressure valves or a positive pressure valve therein.
2. Description of the Prior Art
As conventional positive-negative pressure valves or a positive pressure valve contained in a filler neck cap, there have been proposed various kinds of caps having different configurations for assembling valve components in narrow spaces to compact the sizes of the caps and ensure smooth operations of the valves, for example, as disclosed in U.S. Pat No. 3,724,707, U.S. Pat No. 4,091,955, U.S. Pat. No. 4,162,021, U.S. Pat. No. 4,676,390, and U.S. Pat. No. 4,716,920.
The inventor of the present application has previously developed such filler neck caps as shown in FIGS. 6 and 7 as a result of investigation in various ways, for the purpose of achieving the above objects to assemble the valve components in the narrow spaces and to obtain the smooth operations of the valves. FIGS. 6 and 7 are vertical cross-sectional views of the filler neck caps of the positive-negative pressure valve type and of the positive pressure valve type in the prior art. The valve employed in each conventional filler neck cap illustrated in FIGS. 6 and 7 is arranged in such a manner that a partition or separation plate 11 within an inner cap 2 of the filler neck cap operates as a valve seat and a valve body 6 is compressed against the separation plate by means of a coil spring 4 so that the valve body may contact to overlap the separation plate.
In the above case, if the valve body or a valve body retainer plate 5 is formed into a configuration of a plate-like member, the space for accommodation of the plate-like members has to be enlarged. In addition, when the plate-like valve body is brought into contact with the valve body retainer plate without a gap therebetween, a disadvantage appears such that a sealing effect of the valve body at low pressure is deteriorated. Further, even if the valve body and the valve body retainer plate are so improved as to produce a space therebetween, the valve body sticks to the valve body retainer plate on the negative pressure side, which also results in a deterioration of the sealing effect of the valve body. It has clearly be seen that the relation between the valve body and the valve body retainer plate in the narrow space and the difference in the constructions thereof delicately affect on the sealing effect of the valve body.
In order to provide a mechanical strength for the valve body and accommodate the valve body in the restricted space, the valve body retainer plate has been formed into a hat-like shape, and the valve body has been similarly into a pan-like configuration setting the opening side down, for being contained within the hat-like valve body retainer plate. However, a problem to be solved was found in that, when strong flow of gas was created at the time of opening the valve body, a violent vibration was produced, thereby causing the unstable flow rate of the gas as well as a granting noise of the filler neck cap.